Aluminum (Al3+) wastewater mainly includes all kinds of Aluminum surface treatment liquid which strictly prohibited to emission directly due to its strong acid.
Most of factories and enterprises are mostly used to add water to dilute or alkali neutralization. This extensive processing method, not only cause a part of the aluminum ions being discharge directly, but also a large number of harmful petal ions and heavy metal ions is discharged directly. In this way, a large amount of water and alkali can be consumed, at the same time, surface water, groundwater and ground field is possible to be polluted by a large volume of wastewater.
Shi reports his research results that proposed to extract aluminum ion (Al3+) from aluminum foil treatment wastewater to prepare polyaluminum chloride (Poly-Aluminum Chloride, PAC), the final utilization of other wastewater as flocculants. However, he couldn't dodge a central question indeed in the aluminum (Al3+) wastewater often content a certain amount of other metal cations such as calcium, iron, copper, sodium or even, heavy metal cations. These impurities continue to exist in the flocculant while water purification, this may cause secondary pollution.
In recent years, there are gradually development of aluminum (Al3+) waste water which reused for making some industrial products, such as aluminum sulfate, aluminum carbonate, polymeric ferric aluminum chloride, intends to achieve wastewater resourceful recycling. But lack of these methods obvious those products that reused from waste water are mostly low quality, low value-added products. Indeed, these products are very difficult to gain enough revenue to support cost of wastewater resourceful recycling, this wouldn't make the recycling of wastewater effectively and stably.
Some researchers have proposed to treat waste water by using ion exchange method, such as the use of ion exchange resin for recovery of aluminium (Al3+) ion. This method not only due to the ion exchange resin itself has the preferential adsorption of different ions, lead to filter only partially ions, not to completely purify wastewater. Especially, the long time adsorption, non-stable adsorption amount, and the costly of ion exchange resin increase the economic burden of factories and enterprises.
Ultra high purity nano alumina has the advantages of high density, high melting point, high hardness and good chemical stability, it is widely used on a variety of optical devices, window materials sapphire substrate materials in emerging high-tech industries, but alumina powder conventionally produced from bauxite ore by Bayer process, this production process simple, extensive and large energy consumption and can only produce the purity of the alumina at around 98%-99%, coarse particles is mostly in bigger than 10 μm and particle size distribution is not uniform, so the Bayer products are mainly provide for aluminum reduction process. Base on Bayer process, many methods have emerged such as aluminum ammonium sulfate, aluminium alkoxide method, flame sintering in high temperature method and so on, all these methods have a big cost on their raw materials, such as aluminum sulfate ammonium method using high purity aluminium hydroxide, aluminium alkoxide method using the high purity aluminum block, high temperature sintering method using high purity aluminum powder. At the same time, large amount of harmful gases volatile such as nitrogen oxides, sulfur monoxide, sulfur dioxide, hydrogen sulfide and isopropanol in the heat treatment process. These methods generally have the high cost of raw materials, big pollution of the production process, alumina particle size hard to control.